1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly, to a method for performing communication using a frame structure supporting H-FDD operation and a device using the same.
2. Discussion of the Related Art
An IEEE 802.16m system can support both a frequency division duplex (FDD) scheme that includes a half-frequency division duplex (H-FDD) user equipment operation and a time division duplex (TDD) scheme. The IEEE 802.16m system uses an orthogonal frequency division multiplexing access (OFDMA) as a multiplex access mode in a downlink and an uplink.
Hereinafter, a frame structure of the IEEE 802.16m system will be described in brief.
FIG. 1 is a diagram illustrating a structure of a basic frame in an IEEE 802.16m system.
Referring to FIG. 1, each superframe of 20 ms includes four same sized radio frames of 5 ms, and starts with a superframe header (SFH). If any one of channel bandwidths 5 MHz, 10 MHz, and 20 MHz is provided, each radio frame of 5 ms includes eight subframes. One subframe can be allocated for downlink or uplink transmission. The subframes can be defined in such a manner that the first type subframe includes six OFDMA symbols, the second type subframe includes seven OFDMA symbols, and the third type subframe includes six OFDMA symbols.
The basic frame structure can be applied to both the FDD scheme and the TDD scheme including H-FDD user equipment operation. In the TDD system, two switching points exist at each radio frame. The switching points can be defined in accordance with directional variation from the downlink to the uplink or from the uplink to the downlink.
The H-FDD user equipment can be included in the FDD system, and a frame structure is similar to a TDD frame structure in view of the H-FDD user equipment. However, downlink and uplink transmission occurs at two separate frequency bandwidths. Transmission gaps between the downlink and the uplink are required for switching of transmitting and receiving circuits.
FIG. 2 is a diagram illustrating an example of an FDD frame structure for channel bandwidths of 5 MHz, 10 MHz, and 20 MHz and having a CP length corresponding to ⅛ of a useful symbol length.
Referring to FIG. 2, a base station that supports an FDD scheme can support a half-duplex user equipment and a full-duplex user equipment at the same time, wherein the half-duplex user equipment and the full-duplex user equipment are operated using the same radio frequency (RF) carrier. A user equipment that supports an FDD scheme should use any one of H-FDD scheme and FDD scheme. For both downlink transmission and uplink transmission, all subframes can be used. Downlink and uplink transmission can be divided in a frequency domain. One superframe is divided into four frames, wherein one frame includes eight subframes.
As described above, the IEEE 802.16m system should support both the H-FDD scheme and a full-frequency division duplex (F-FDD) scheme. However, an FDD frame structure for improving system throughput to the maximum range has not been suggested until now.